Pallet container

ABSTRACT

A pallet container for the storage and transport of liquid or free-flowing goods, includes a thin-walled inner container of thermoplastic material, a tubular lattice frame closely surrounding the inner plastic container in the form of a support jacket, and a bottom pallet upon which the inner plastic container rests and with which the tubular lattice frame is securely fixed. The inner plastic container includes for withdrawal of liquid goods at the lower side, approximately in mid-section in a side wall near its bottom a blown, calibrated tubular pipe for allowing attachment of a closeable discharge fitting which is fixedly welded with its tubular housing to the calibrated tubular pipe of the inner container.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of prior filed copending PCTInternational application no. PCT/EP2005/002039, filed Feb. 25, 2005,which designated the United States and on which priority is claimedunder 35 U.S.C. §120, and which claims the priority of German PatentApplication, Serial No. 20 2004 003 236.8, filed Feb. 27, 2004, pursuantto 35 U.S.C. 119(a)-(d), the subject matter of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

The present invention relates, in general, to a pallet container for thestorage and transport of liquid or free-flowing goods. The presentinvention further relates to a method of making such a pallet container.

The structural configuration of such pallet containers is generallyknown and its essential components are described e.g. in Germanpublication no. DE-A 34 42 701. Typically, discharge fittings arescrewed by means of a coupling nut onto an outer thread of the outletpipe of the inner container; known are however also further weld-onconnections for discharge fittings. A pallet container with a dischargefitting welded directly onto the inner plastic container is known, e.g.,from German publication no. DE-A 34 42 700. Following the blow-moldingprocess, a bottom-proximal opening is hereby provided in the innercontainer for insertion of about half of the housing of the dischargefitting and welded against the wall of the inner container.

Further known from the prior art are constructions with pre-fabricatedthreaded pipes or entire housings for fittings as insert into the openedblow mold with subsequent welding with the plastic container during theblow-molding process. These constructive variations suffer howeverparticular drawbacks:

-   -   The placement of the threaded pipe or housing into the blow mold        is complicated and not safe,    -   welding of the insert with the inner container during blow        molding process is comparably undefined (no precisely        controllable contact pressure),    -   the through-flow opening in the inner container must be opened        subsequently through the pipe or the valve housing (e.g.        drilling with respective contamination)    -   the fitting must be completed on the container (complex);    -   testing the critical component “fitting” can only be implemented        on the container itself.    -   the constructions with fittings directly welded onto the        container wall represent a particular variant which does not        allow use of the inner container for threadable fittings; this        is e.g. disadvantageous for later reconditioning.

The construction, known from German publication no. DE-A 34 42 700 withattached connection for the discharge fitting by welding, has thefollowing drawbacks:

-   -   the fabrication process of the inner container is suited        especially to the type of construction of a sliding-type        fitting;    -   the discharge opening is incorporated subsequently into the        inner container, i.e. after the blow-molding process but before        welding the discharge fitting,    -   the region of the inner container for welding of the discharge        fitting is blown without additional aids, i.e. the thin wall        thicknesses result from the blowing process and are subject to        the typical fluctuations with insufficient reproducibility and        slight stability (bending strength),    -   the construction of the inner container represents a special        variant which is not applicable for fittings that can be screwed        on.

European publication no. EP-A 0 704 385 discloses a pallet container inwhich the threaded pipe is placed as pre-fabricated injection-moldedpart into the blow mold and welded onto the inner plastic container,wherein the discharge fitting is subsequently screwed on by means of acoupling nut.

It would therefore be desirable and advantageous to provide an improvedpallet container to obviate prior art shortcomings and to construct apallet container with an inner container that allows cost-efficientmanufacturing of the connection for a discharge fitting and has aparticularly high load-bearing capability (bending strength) when thedischarge fitting is handled for withdrawing goods.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a pallet container forthe storage and transport of liquid or free-flowing goods, including athin-walled inner container of thermoplastic material, a tubular latticeframe closely surrounding the inner plastic container in the form of asupport jacket, and a bottom pallet upon which the inner plasticcontainer rests and with which the tubular lattice frame is securelyfixed, wherein the inner plastic container includes for withdrawal ofliquid goods at a lower side, approximately in mid-section in a sidewall near the bottom plate a blown, calibrated tubular pipe for allowingattachment of a closeable discharge fitting wherein the dischargefitting is fixedly welded or bonded with its tubular housing to thetubular pipe of the inner container.

The present invention resolves prior art problems by providing a fittingwhich is fixedly connected to the pipe of the inner container by meansof welding or bonding. When a welded connection is involved, variousprocesses can be used, such as hot plate welding, laser welding,friction welding, ultrasonic welding, or vibration welding. Hot platewelding is used in a preferred embodiment because it is very economicalwhile providing easy access to the welding spot. However, also bondingby means of a special plastics adhesive can be executed in a simple andinexpensive manner. In contrast to the use of a coupling nut to screwthe discharge fitting connections onto the outlet pipe, a fixedconnection has the following advantages:

-   -   Higher safety: screw connections and in particular the        necessarily used ring seals always pose a risk potential for        leakage. Seals used heretofore have either poor sealing        capabilities (slight rebound capability, cold flow, high        hardness) or no universal chemically resistance (aging,        brittleness);    -   Threadable connections with components of plastic (here in any        event the outlet pipe) are subject to a decrease of the        tightening moment in view of the cold flow and thus may become        leaky;    -   Less costs: When fixedly connected by means of bonding or        welding, the need for the coupling nut and the ring seal is        eliminated (cost savings);    -   The discharge fitting is connected with the inner container        preferably in complete and pre-checked conditions.

Hereby, all types of constructions of discharge fittings, such as e.g.flap valve, sliding valve, ball valve, etc, may advantageously beapplicable.

The connection during welding (or bonding) of fitting and innercontainer is implemented after the blow molding process on the cooledinner plastic container in a separate working step under reproducible,controlled joining conditions such as, e.g. optimum joining time,joining temperature, joining pressure, etc.

In contrast to threads simply blown onto blow-molded parts (imprecisethread formation, poor reproducibility), calibrated threaded pipes havegood reproducibility with exact formation of the outer thread turns(just like in an injection molding process) because the threaded pipe isheld on the inside on the blow pin and the thread is pressed and formedon the outside by a split threaded calibration piece in the moldpartition plane of the two-part blow mold or a respective mold slide.

The components inner container and fitting have the following features:

-   -   The inner container with outlet pipe attached by calibration        does not require additional finishing works of the inner        container to produce the discharge opening; this is realized        during the blowing process itself.    -   Defined wall thicknesses (outer and inner contours defined by        mold insert or blow pin needle, respectively) can be realized in        the outlet pipe.    -   In the region of the outlet pipe, reproducibly limited,        increased wall thicknesses of the inner container can be        realized, combined with gain in strength and gain in material        for the subsequent welding. The direct contact surface for        welding can be configured substantially freely and can be        optimized for welding.    -   During welding operation (or bonding operation), the calibrated        threaded pipe is held in a tongs-like fixing device having two        semi-shells with internal thread for precise engagement in the        outer thread of the outlet pipe, so that a high contact pressure        can be applied during welding.

According to another feature of the present invention, the contactsurface of the blown outlet pipe (with outer thread) for the welding maybe provided with inwardly descending slant, thereby realizing a bettermelting of the plastic material.

According to another feature of the present invention, the contactsurface of the blown outlet pipe (e.g. with flanged rim) for the weldingmay be configured of flat design. Advantageously, the outer contour ofthe calibrated pipe is hereby configured such that a secure mechanicalresistance is established for applying the required mechanical joiningpressure for some welding processes (e.g. hot plate welding).

The welded connections eliminate the ring seal and coupling nut; theyrepresent a significantly lesser error source for leakage because thetypically used ring seal ages very often or is attacked by aggressivecontents (e.g. swelling, embrittling).

According to another feature of the present invention, the contactsurface of the calibrated outlet pipe may be provided with a screwthread (universal pipe!).

During welding operation, a tool for securing the outlet pipe engagesits outer thread so that a high joining pressure can be applied whenwelding the tubular connection piece of the discharge fitting.

These thus-configured inner containers can thus be used for screwed-onor welded-on discharge fittings. The following advantage results hereby:Weld-on discharge fittings can be removed during reconditioning throughsimple mechanical separation of the fixedly interconnected componentsoutlet valve and inner container and very easily replaced for furtherutilization by a screwed-on fitting with seal and coupling nut, aspracticed currently in typical pallet containers.

The discharge fitting according to the invention of plastic ispreferably configured with extended inlet pipe having a diameter(external e.g. 62.5 mm) which is as closely suited as possible to theinner diameter of the outlet pipe (about 63.5 mm) so as to allow aprecision fit and problem-free joining with optimum material fusion onthe welding surfaces. The outlet pipe has a length of about 20 to 50 mm,preferably about 35 mm.

The extended inlet pipe (about 20 to 40 mm, preferably about 30 mm)resists encountered forces during mechanical loads when tested (inparticular drop test) and application (attachment of hose connections orother couplings on the discharge fitting) and relieves thereby thewelded connection (high bending strength). The configuration of thedischarge fitting is designed in the area of welding (inlet pipe andwelding flange) preferably such that the same fitting construction withrespective coupling nut and seal can find application as threadablefitting.

The round connection piece of the discharge fitting with welding flangeis welded to the end surface of the outlet pipe calibrated onto theinner plastic container. This end surface of the outlet pipe ispreferably slanted from outside inwardly so that the slanted tip of theslant is initially melted during welding to thereby compensatetolerances of the outlet pipe as caused during blow molding. The outercontour of the calibrated pipe with flange rim or outer thread isconfigured such that a secure mechanical resistance is established forapplying the necessary mechanical joining pressure for the weldingoperation.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be morereadily apparent upon reading the following description of currentlypreferred exemplified embodiments of the invention with reference to theaccompanying drawing, in which:

FIG. 1 is a side elevation of a pallet container according to thepresent invention;

FIG. 2 is a longitudinal section of a discharge fitting for use in thepallet container;

FIG. 3 is a front view of a discharge fitting;

FIG. 4 is a longitudinal section of the discharge fitting, taken alongthe line A-A in FIG. 3;

FIG. 5 a is a side view of the discharge fitting before welding;

FIG. 5 b is a side view of the discharge fitting after welding; and

FIG. 6 is a perspective view of the discharge fitting

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the Figures, same or corresponding elements are generallyindicated by same reference numerals. These depicted embodiments are tobe understood as illustrative of the invention and not as limiting inany way. It should also be understood that the drawings are notnecessarily to scale and that the embodiments are sometimes illustratedby graphic symbols, phantom lines, diagrammatic representations andfragmentary views. In certain instances, details which are not necessaryfor an understanding of the present invention or which render otherdetails difficult to perceive may have been omitted.

Turning now to the drawing, and in particular to FIG. 1, there is showna side elevation of a pallet container according to the presentinvention, generally designated by reference numeral 10. The palletcontainer 10 has a thin-walled inner container 12 of thermoplasticmaterial, a tubular lattice frame 14 closely surrounding the innerplastic container 12 as support jacket, and a bottom pallet 16 on whichthe inner plastic container 12 rests and with which the tubular latticeframe 14 is securely connected. The inner plastic container 12 includesfor withdrawal of liquid goods at the lower side, approximately inmid-section in a side wall near its bottom a blown, a calibrated tubularpipe 18 with outer thread 20 for allowing attachment of a closeabledischarge fitting 22. The pipe 18 may, however, also be provided with aflange rim on which the discharge fitting 22 is secured by means of atensioning clamp, wherein the discharge fitting 22 may be designed asflap valve, sliding valve, or ball valve.

The discharge fitting 22, which is shown in greater detail in FIG. 2, ismade substantially of plastic and equipped according to an exemplifiedembodiment with a flap valve closure, actuatable by a rotary grip 30,and is closed on the outside with a screw cap 32. The discharge fitting22 has a housing 24 which is provided on the container side with aninlet pipe 26 which is inserted at precision fit in the pipe 18 up toits flange ring 28. In the lower half of FIG. 2, the pipe 18 with outerthread 20 is slightly set back in relation to the flange ring 28(situation before welding), while the upper half of FIG. 2 shows thepipe 18 bearing upon the flange rim 28 of the housing 24 of thedischarge fitting 22 and securely welded therewith (situation afterwelding).

In view of a good accessibility and optimum geometries of welding spots,the cost-efficient hot plate welding process is preferably used for thewelding operation. The discharge fitting is hereby welded onto theoutlet pipe in a complete and pre-checked state. The inner container,withdrawn from the blow mold, does not require any refinishing of thepipe for the welding operation.

The thin-walled inner plastic container 12 typically has a mean wallthickness of about 3 mm, while the calibrated pipe 18 for the dischargefitting 22 has a wall thickness of about 5 mm, when a configuration withan inner diameter of about 63 mm is involved. The constructiveadvantages of the configuration according to the invention are asfollows: calibrated pipe with proper material thickness for welding andjoining contour; standard pipe with outer thread for attachment of therespectively desired discharge fitting by screwing or welding; longinlet and relief pipes on the fitting with high load-bearing capabilityfor bending stress during frequent operation of the rotary valve.

For viscous goods, pipes and discharge fittings of greater nominal widthor greater diameter of about 80 mm or even 120 mm to 150 mm may beprovided. Hereby, it is shown: the greater the diameter, the better andsafer a fixed connection (welded or bonded) of pipe and dischargefitting in comparison to a conventional screw connection.

FIG. 3 is a front view of the discharge fitting 22, showing inparticular the front screw cap 32 and the rotary grip 30. FIG. 4 shows alongitudinal section along the line A-A of this discharge fitting 22. Asupport device 38, which is prefabricated as a separate injection-moldedpart and includes an annular outer rim and a star-shaped or cross-shapedinner part, is inserted on the container-side securely into the inletpipe 26 of the discharge fitting 22. This cross-shaped support device 38(injection-molded plastic part with fiber reinforcement) is provided toprevent the pipe 18 from assuming an oval shape which could potentiallyoccur as a result of warping or shrinkage, when the inner plasticcontainer unevenly cools down in this region.

FIG. 5 a shows again the container pipe 18 with outer thread 20 and thedischarge fitting 22 before insertion and before welding, whereas FIG. 5b shows the welded state. The inlet pipe 26 is hereby pushed into thepipe 18 up to the flange ring 28, and the end surface of the pipe isfixedly welded to the flange ring 28. Refinishing work of the weldedseam is hereby not necessary.

FIG. 6 shows again by way of perspective view the cross-shaped supportdevice 38 which is arranged in the inlet pipe 28 and extendstransversely to the diameter and which is configured here in one pieceand integrated in the housing 22 of the discharge fitting 22.

In accordance with a particular variation, the pallet container isprovided for use in potentially explosive zones or for use withcombustible goods; in this case, the inner container is configuredantistatically or electrically diverting on the outside, and the housingof the discharge fitting is also made of electrically conductive plasticand provided with a connection 34 for threaded attachment of a groundcable (compare FIG. 2).

The particular advantage of this present invention resides also in thefact that a “normal” inner plastic container with calibrated pipe 18 andouter thread 20 is used for welding the discharge fitting thereto; thereare no modifications necessary on the blow mold or the blown part (innercontainer). Thus, customer's desires can easily be satisfied, regardlesswhether a pallet container is desired with typical discharge fittingwhich is screwed on by means of a coupling nut or is fixedly welded in.Also, a pallet container with fixedly welded discharge fitting can bereused again. Reconditioning requires only a simple separation of thewelded discharge fitting, an internal milling of the pipes, and a newfitting can be screwed on or welded in.

A pallet container with welded discharge fitting can be used for almostany aggressive goods because there is no need to consider thesusceptibility of the seal that is no longer necessary.

While the invention has been illustrated and described in connectionwith currently preferred embodiments shown and described in detail, itis not intended to be limited to the details shown since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention. The embodiments werechosen and described in order to best explain the principles of theinvention and practical application to thereby enable a person skilledin the art to best utilize the invention and various embodiments withvarious modifications as are suited to the particular use contemplated.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims and includes equivalents of theelements recited therein:

1. A pallet container for the storage and transport of liquid orfree-flowing goods, comprising a thin-walled inner container ofthermoplastic material, a tubular lattice frame closely surrounding theinner plastic container in the form of a support jacket, and a bottompallet upon which the inner plastic container rests and with which thetubular lattice frame is securely fixed, wherein the inner plasticcontainer includes for withdrawal of liquid goods at a lower side,approximately in mid-section in a side wall near the bottom plate ablown, calibrated tubular pipe for allowing attachment of a closeabledischarge fitting wherein the discharge fitting is fixedly welded orbonded with its tubular housing to the tubular pipe of the innercontainer.
 2. The pallet container of claim 1, wherein the dischargefitting is welded by means of a process selected from the groupconsisting of hot plate welding, laser welding, friction welding,ultrasonic welding, or vibration welding, to the tubular pipe of theinner plastic container.
 3. The pallet container of claim 1, wherein thehousing of the discharge fitting is designed on the side of the innerplastic container as extended tubular inlet pipe with a circumferentialflange ring, wherein the inlet pipe is inserted into the tubular pipe ofthe inner plastic container, and the flange ring is welded to an endsurface of the tubular pipe].
 4. The pallet container of claim 1,wherein the housing of the discharge fitting is designed on the side ofthe inner plastic container as extended tubular inlet pipe with acircumferential flange ring, wherein the inlet pipe is inserted into thetubular pipe of the inner plastic container, and the flange ring isbonded to an end surface of the tubular pipe.
 5. The pallet container ofclaim 1, wherein the tubular pipe of the inner plastic container isprovided with an outer thread (20) and has a length of about 20 mm to 50mm.
 6. The pallet container of claim 5, wherein the tubular pipe has alength of about 35 mm.
 7. The pallet container of claim 1, wherein thehousing of the discharge fitting is designed on the side of the innerplastic container as extended tubular inlet pipe with a circumferentialflange ring, wherein the inlet pipe of the discharge fitting has alength of about 20 mm to 40 mm up to the flange ring.
 8. The palletcontainer of claim 7, wherein the inlet pipe of the discharge fittinghas a length of about 30 mm up to the flange ring.
 9. The palletcontainer of claim 1, wherein the tubular pipe of the inner plasticcontainer has a slant at its end surface.
 10. The pallet container ofclaim 7, wherein the inlet pipe of the discharge fitting has integratedtherein a support device extending transversely to a diameter of theinlet pipe.
 11. The pallet container of claim 10, wherein the supportdevice is prefabricated as separate injection-molded part and has aring-shaped outer rim which is securely received in the inlet pipe ofthe discharge fitting.
 12. The pallet container of claim 1, wherein thehousing of the discharge fitting is made of electrically conductingplastic and is provided with a connection for a screwed attachment of aground cable.
 13. A pallet container for the storage and transport ofliquid or free-flowing goods, comprising: a bottom plate; an innercontainer made of thermoplastic material and resting on the bottomplate, said inner container having a side wall formed with a blown,calibrated tubular pipe approximately in mid-section thereof near thebottom plate; a tubular lattice frame closely surrounding the innerplastic container and securely fixed to the bottom plate; and acloseable discharge fitting non-detachably connected to the tubular pipeof the inner container.
 14. The pallet container of claim 13, whereinthe discharge fitting is welded to the tubular pipe.
 15. The palletcontainer of claim 13, wherein the discharge fitting is bonded to thetubular pipe.
 16. A method of making a pallet container for the storageand transport of liquid or free-flowing goods, comprising a thin-walledinner container of thermoplastic material, a tubular lattice frameclosely surrounding the inner plastic container in the form of a supportjacket, and a bottom pallet upon which the inner plastic container restsand with which the tubular lattice frame is securely fixed, wherein theinner plastic container includes for withdrawal of liquid goods at alower side, approximately in mid-section in a side wall near the bottomplate a blown, calibrated tubular pipe for allowing attachment of acloseable discharge fitting, wherein the inner plastic container is heldby a correspondingly shaped holding device which attaches to thecalibrated tubular pipe, and the housing of the discharge fitting isconfigured with an extended tubular inlet pipe with circumferentialflange rim for insertion into the tubular pipe up to the flange ring,and the end surface of the tubular pipe is welded or bonded to theflange ring by applying a respective joining pressure upon both parts.17. The method of claim 16, wherein the discharge fitting is connectedto the inner container in a complete and pre-checked state.
 18. A methodof making a pallet container for the storage and transport of liquid orfree-flowing goods, comprising the steps of: placing a support device ina tubular pipe of an inner container of thermoplastic material;providing a discharge fitting with a tubular inlet pipe having acircumferential flange ring; inserting the inlet pipe of the dischargefitting into the tubular pipe until the flange ring bears against thetubular pipe; and non-detachably connecting the flange ring to an endsurface of the tubular pipe.
 19. The method of claim 18, wherein theflange ring is welded to the end surface of the tubular pipe.
 20. Themethod of claim 18, wherein the flange ring is bonded to the end surfaceof the tubular pipe.